Methods and systems for alignment of ophthalmic imaging devices

ABSTRACT

Ophthalmic imaging systems and related methods provide pseudo feedback to aid a user in aligning the user&#39;s eye with an optical axis of the imaging system. An ophthalmic imaging system includes an ophthalmic imaging device having an optical axis, a display device, an eye camera, and a control unit. The display device displays a fixation target viewable by the user. The eye camera images the eye to generate eye image data. The control unit processes the eye image data to determine a position of the eye relative to the optical axis, processes the position of the eye relative to the optical axis to generate a pseudo position of the eye relative to the optical axis, and causes the display device to display an indication that provides feedback to the user that the eye is located at the pseudo position of the eye relative to the optical axis.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/425,362 filed May 29, 2019, which is a continuation of InternationalApplication No. PCT/IL2018/051172, filed Nov. 4, 2018, which claims thebenefit of U.S. Provisional Application Ser. No. 62,582,779, filed onNov. 7, 2017, the entire contents of which are hereby incorporated byreference in their entirety for all purposes.

BACKGROUND

Macular degeneration is the leading cause of vision loss in the UnitedStates of America. In macular degeneration, the central portion of theretina (a.k.a., the macula) deteriorates. When healthy, the maculacollects and sends highly detailed images to the brain via the opticnerve. In early stages, macular degeneration typically does notsignificantly affect vision. If macular degeneration progresses beyondthe early stages, vision becomes wavy and/or blurred. If maculardegeneration continues to progress to advanced stages, central visionmay be lost.

Although macular degeneration is currently considered to be incurable,treatments do exist that may slow the progression of the disease so asto prevent severe loss of vision. Treatment options include injection ofan anti-angiogenic drug into the eye, laser therapy to destroy anactively growing abnormal blood vessel(s), and photodynamic lasertherapy, which employs a light-sensitive drug to damage an abnormalblood vessel(s). Early detection of macular degeneration is of paramountimportance in preventing advanced progression of macular degenerationprior to treatment to inhibit progression of the disease.

Early detection of macular degeneration can be accomplished using asuitable retinal imaging system. For example, Optical CoherenceTomography (OCT) is a non-invasive imaging technique relying on lowcoherence interferometry that can be used to generate a cross-sectionalimage of the macula. The cross-sectional view of the macula shows if thelayers of the macula are distorted and can be used to monitor whetherdistortion of the layers of the macula has increased or decreasedrelative to an earlier cross-sectional image to assess the impact oftreatment of the macular degeneration.

Existing OCT imaging systems, however, are typically expensive and mayhave to be operated by a trained technician. For example, a trainedtechnician may be required to properly align an optical axis of the OCTimaging system with the optical axis of the eye examined. As a result,the use of such OCT imaging systems is typically restricted tospecialized eye care clinics, thereby limiting use of such OCT imagingsystems for widespread screening for early stage macular degeneration.

BRIEF SUMMARY

The following presents a simplified summary of some embodiments of theinvention in order to provide a basic understanding of the invention.This summary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome embodiments of the invention in a simplified form as a prelude tothe more detailed description that is presented later.

Ophthalmic imaging systems and related methods employ improved feedbackto a user for use in self-alignment of the user's eye with the opticalaxis of the ophthalmic imaging system. In many embodiments, the userlooks into a view port of the imaging device and is instructed to lookat a fixation target, and perform a task. In some embodiments of theophthalmic imaging systems and related methods disclosed herein, theuser is shown two fiducials, one representing the optical axis of thedevice and the other one represents the center of the pupil and the taskis to move “pupil” fiducial till the two are coincident. In someembodiments of the ophthalmic imaging systems and related methodsdisclosed herein, the fiducial representing the center of the pupil isdisplayed at a location that is, in many instances, offset by acontrolled amount from where the fiducial would be displayed to indicatethe actual position of the user's pupil relative to the optical axis ofthe imaging system. Showing an eye position fiducial at a location thatis offset by a controlled amount from a location that would indicate theactual position of the user's pupil relative to the optical axis is incontrast to existing approaches. By displaying the eye position fiducialat a location that is offset by a controlled amount from a location atwhich the fiducial would be displayed to indicate the actual position ofthe user's pupil relative to the optical axis, the effort required bythe user to achieve and maintain sufficient positioning of the user'spupil relative to the optical axis of the imaging device is reducedrelative to prior approaches. For example, in some embodiments, the eyeposition fiducial is displayed coincident with optical axis fiducialwhen the actual position of the pupil is close enough to the opticalaxis to enable satisfactory imaging of the user's eye so as to avoidfeedback to the user that may induce the user to try to reposition theuser's eye when the current position of the user's eye is sufficientlyclose to the optical axis.

Thus, in one aspect, an ophthalmic imaging system includes an ophthalmicimaging device, a display device, an eye camera, and a control unit. Theophthalmic imaging device has an optical axis. The display devicedisplays a fixation target viewable by an eye of a user. The eye camerais operable to image the eye to generate eye image data. The controlunit processes the eye image data to determine a position of the eyerelative to the optical axis. The control unit processes the position ofthe eye relative to the optical axis to generate a pseudo position ofthe eye relative to the optical axis. The pseudo position of the eyerelative to the optical axis is different from the position of the eyerelative to the optical axis. The control unit causes the display deviceto display an indication that provides feedback to the user that the eyeis located at the pseudo position of the eye relative to the opticalaxis.

In many embodiments of the ophthalmic imaging system, the indication isdisplayed at a position relative to the fixation target. For example,the indication displayed to the user can include an eye pseudo positionindicator displayed at a position relative to the fixation targetmatching the pseudo position of the eye relative to the optical axis. Inmany embodiments, if a distance between the position of the eye and theoptical axis is less than an acceptable distance, the pseudo position ofthe eye relative to the optical axis is generated to lie on the opticalaxis. In many embodiments, the indication displayed to the user includesan eye pseudo position indicator displayed aligned with the fixationtarget to provide feedback to the user indicating that the position ofthe eye is located on the optical axis.

In some embodiments of the ophthalmic imaging system, the indicationdisplayed to the user is based on a size of a pupil of the eye. In someembodiments, the acceptable distance is a function of the size of thepupil. For example, in some embodiments of the ophthalmic imagingsystem, the acceptable distance is smaller for a relatively small pupiland larger for a relatively large pupil. In some embodiments, thecontrol unit processes the eye image data to determine the size of thepupil of the eye.

In some embodiments of the ophthalmic imaging system, the acceptabledistance is increased in response to user achieving alignment of the eyeof the user with the optical axis. For example, the acceptable distancecan be set equal to a pre-alignment acceptable distance prior to theposition of the eye being repositioned from being greater than thepre-alignment acceptable distance from the optical axis to being equalto or less than the pre-alignment acceptable distance from the opticalaxis. The acceptable distance can then be reset to a post-alignmentacceptable distance in response to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis, thepost-alignment acceptable distance being greater than the pre-alignmentacceptable distance.

In some embodiments of the ophthalmic imaging system, the pre-alignmentacceptable distance is based on a size of a pupil of the eye and/or thepost-alignment acceptable distance is based on a size of a pupil of theeye. In some embodiments of the ophthalmic imaging system, the controlunit processes the eye image data to determine the size of the pupil ofthe eye.

In some embodiments of the ophthalmic imaging system, the control unitis configured to detect the position of the eye even if a portion of apupil of the eye is obscured. For example, in some embodiments, thecontrol unit is configured to process the eye image data to (a) detectif a portion of the pupil of the eye is obscured, (b) identify anunobscured portion of the pupil, and (c) determine the position of theeye relative to the optical axis based on the unobscured portion of thepupil.

In many embodiments of the ophthalmic imaging system, the position ofthe eye relative to the optical axis is repeatedly determined to trackthe position of the eye relative to the optical axis. For example, inmany embodiments the eye camera captures a series of images of the eyeand the eye image data includes image data for each of the series ofimages of the eyes. In many embodiments, for each image of the series ofimages of the eye, the control unit (a) processes the eye image data todetermine a respective position of the eye relative to the optical axis,(b) processes the respective position of the eye relative to the opticalaxis to generate a respective pseudo position of the eye relative to theoptical axis, and (c) causes the display device to display a respectiveindication that provides feedback to the user that the eye is located atthe respective pseudo position of the eye relative to the optical axis.In many embodiments, the respective pseudo position of the eye relativeto the optical axis is different from the respective position of the eyerelative to the optical axis. In many embodiments, the control unitprocesses, for the series of images of the eye, a series of positions ofthe eye relative to the optical axis to detect if the user fails toachieve and/or maintain acceptable positioning of the eye relative tothe optical axis. In many embodiments, the control unit, in response todetecting failure of the user to achieve and/or maintain acceptablepositioning of the eye relative to the optical axis, increases a size ofthe fixation target and/or the indication displayed to the user thatprovides the feedback to the user.

In many embodiments of the ophthalmic imaging system, the pseudoposition of the eye is generated as a function of the position of theeye relative to the optical axis. For example, in some embodiments thecontroller includes a proportional controller and generation of thepseudo position of the eye relative to the optical axis by the controlunit comprises multiplying, by the proportional controller, the positionof the eye relative to the optical axis by a gain factor not equal to1.0.

In many embodiments, if a distance of the eye relative to the opticalaxis is less than an acceptable distance, the pseudo position of the eyerelative to the optical axis is generated to lie on the optical axis. Inmany embodiments, the indication displayed to the user includes an eyepseudo position indicator displayed aligned with the fixation target toprovide feedback to the user indicating that the eye is located on theoptical axis. For example, if the eye and the optical axis are notperfectly aligned but the offset between the optical axis and the pupilis small enough such that an imaging beam of the ophthalmic imagingdevice enters the pupil without any clipping, the user can be providedfeedback that the user's eye is actually aligned with the optical axisso as to induce the user to hold still and avoid frustrating the uservia providing feedback to the user suggesting that repositioning by theuser is required when no repositioning by the user is actually required.The size of the acceptable offset between the actual position of theuser's eye and the optical axis can be dependent on the beam diameter ofthe ophthalmic imaging device projected to the eye and the pupildiameter. For example, the acceptable offset can be provided by equation(1).Acceptable Offset=((Pupil Diameter−Beam Diameter)/2)  Equation (1)

In some embodiments, the acceptable offset may vary from 0.1 mm for acombination of a large beam (2.5 mm) and a small pupil diameter (2.7 mm)to 5.0 mm for a combination of a small beam (0.5 mm) and a large pupil(10.5 mm).

In another aspect, a method of providing feedback to a user of anophthalmic imaging system regarding alignment of an eye of the user withan optical axis of the ophthalmic imaging system is described. Themethod includes displaying a fixation target on a display deviceviewable by the eye of the user. Eye image data corresponding to animage of the eye viewing the fixation target is generated by an eyecamera. A control unit processes the eye image data to determine aposition of the eye relative to the optical axis. The control unitgenerates a pseudo position of the eye relative to the optical axisbased on the position of the eye relative to the optical axis. Thepseudo position of the eye relative to the optical axis is generated tobe different from the position of the eye relative to the optical axis.The control unit causes display of an indication on the display deviceto provide feedback to the user indicating that the eye is located atthe pseudo position of the eye relative to the optical axis.

In many embodiments of the method, the indication is displayed at aposition relative to the fixation target. For example, display of theindication on the display device can include display of a pseudoposition indicator at a position relative to the fixation targetmatching the pseudo position of the eye relative to the optical axis. Inmany embodiments, the method further includes processing the position ofthe eye relative to the optical axis to determine if a distance betweenthe position of the eye and the optical axis is less than acceptabledistance. In many embodiments of the method, the generation of thepseudo position of the eye relative to the optical axis includes settingthe pseudo position of the eye to lie on the optical axis if thedistance of the eye relative to the optical axis is less than theacceptable distance. In many embodiments of the method, the display ofthe indication on the display device includes displaying an eye pseudoposition indicator aligned with the fixation target to provide feedbackto the user that the position of the eye is located on the optical axis.

In some embodiments, the method further includes determining theacceptable distance based on a size of a pupil of the eye. For example,in some embodiments of the method, the acceptable distance is smallerfor a relatively small pupil and larger for a relatively large pupil. Insome embodiments, the method further includes processing the eye imagedata, by the control unit, to determine the size of the pupil of theeye.

In some embodiments of the method, the acceptable distance is increasedin response to user achieving alignment of the eye of the user with theoptical axis. For example, the acceptable distance can be set equal to apre-alignment acceptable distance prior to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis. The acceptabledistance can then be reset to a post-alignment acceptable distance inresponse to the position of the eye being repositioned from beinggreater than the pre-alignment acceptable distance from the optical axisto being equal to or less than the pre-alignment acceptable distancefrom the optical axis, the post-alignment acceptable distance beinggreater than the pre-alignment acceptable distance.

In some embodiments, the method further includes determining thepre-alignment acceptable distance and/or the post-alignment acceptabledistance based on a size of a pupil of the eye. In some embodiments, themethod further includes processing the eye image data, by the controlunit, to determine the size of the pupil of the eye.

In some embodiments of the method, the control unit is configured todetect the position of the eye even if a portion of the pupil isobscured. For example, in some embodiments, the method further includesprocessing the eye image data, by the controller, to (a) detect if aportion of a pupil of the eye is obscured, (b) identify an unobscuredportion of the pupil, and (c) determine the position of the eye relativeto the optical axis based on the unobscured portion of the pupil.

In many embodiments of the method, the position of the eye relative tothe optical axis is repeatedly determined to track the position of theeye relative to the optical axis. For example, in many embodiments, themethod includes generating, by the eye camera, the eye image data so asto comprise image data for each of a series of images of the eyes. Inmany embodiments, the method includes, for each image of the series ofimages of the eye, (a) processing the eye image data, by the controlunit, to determine a respective position of the eye relative to theoptical axis, (b) processing the respective position of the eye relativeto the optical axis, by the control unit, to generate a respectivepseudo position of the eye relative to the optical axis, the respectivepseudo position of the eye relative to the optical axis being differentfrom the respective position of the eye relative to the optical axis,and (c) causing, by the control unit, the display device to display arespective indication that provides feedback to the user that the eye islocated at the respective pseudo position of the eye relative to theoptical axis. In many embodiments, the method includes processing, bythe control unit, for the series of images of the eye, a series ofpositions of the eye relative to the optical axis to detect if the userfails to achieve and/or maintain acceptable positioning of the eyerelative to the optical axis. In many embodiments, the method includes,in response to detecting, by the control unit, failure of the user toachieve and/or maintain acceptable positioning of the eye relative tothe optical axis, increasing, by the control unit, a size of thefixation target and/or the indication displayed to the user thatprovides the feedback to the user.

In many embodiments of the method, the pseudo position of the eye isgenerated as a function of the position of the eye relative to theoptical axis. For example, generating the pseudo position of the eyerelative to the optical axis can include multiplying the position of theeye relative to the optical axis by a factor not equal to 1.0. If adistance of the eye relative to the optical axis is less than anacceptable distance, the pseudo position of the eye relative to theoptical axis can be generated to lie on the optical axis. The indicationdisplayed to the user can include an eye pseudo position indicatordisplayed aligned with the fixation target to provide feedback to theuser that the eye is located on the optical axis.

In another aspect, an ophthalmic imaging system includes an ophthalmicimaging device, a display device, an eye camera, and a control unit. Theophthalmic imaging device has an optical axis. The display devicedisplays a fixation target viewable by an eye of a user. The eye camerais operable to image the eye to generate eye image data. The controlunit processes the eye image data to determine a position of the eyerelative to the optical axis. The control unit causes the display deviceto display an indication that provides feedback to the user that the eyeis located at the position of the eye relative to the optical axis.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the ensuing detailed descriptionand accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a user looking into a view port of an ophthalmic imagingsystem, in accordance with some embodiments.

FIG. 2 is a simplified schematic illustration of an ophthalmic imagingsystem, in accordance with some embodiments.

FIG. 3 is a simplified schematic illustration of another embodiment ofoptical components of the ophthalmic imaging system of FIG. 2.

FIG. 4 is a simplified schematic illustration of a feedback loop thatprovides feedback to a user of an ophthalmic imaging system regardingalignment of the user's eye with an optical axis of the ophthalmicimaging system, in accordance with some embodiments.

FIG. 5 illustrates display of an eye pseudo position indicator relativeto a fixation target, in accordance with some embodiments.

FIG. 6 illustrates display of an eye pseudo position indicatorco-located with a fixation target, in accordance with some embodiments.

FIG. 7 is a simplified schematic block diagrams of acts of a method ofproviding feedback to a user of an ophthalmic imaging system regardingalignment of an eye of the user with an optical axis of the ophthalmicimaging system, in accordance with some embodiments.

FIG. 8 is a simplified schematic block diagrams of additional acts thatcan be practiced in the method of FIG. 7, in accordance with someembodiments.

FIG. 9 illustrates pre-alignment and post-alignment acceptable alignmentareas relative to an imaging area of the ophthalmic imaging system, inaccordance with some embodiments.

FIG. 10 illustrates an acceptable alignment area for a partiallyobscured pupil relative to an imaging area of the ophthalmic imagingsystem, in accordance with some embodiments.

FIG. 11 illustrates pre-alignment and post-alignment acceptablealignment areas for a partially obscured pupil relative to an imagingarea of the ophthalmic imaging system, in accordance with someembodiments.

DETAILED DESCRIPTION

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. However, it will also be apparent toone skilled in the art that the present invention may be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

Referring now to the drawings, in which like reference numeralsrepresent like parts throughout the several views, FIG. 1 shows a user12 looking into a view port 14 of a viewing assembly 16 of an ophthalmicimaging system 10, in accordance with many embodiments. In manyembodiments, the viewing assembly 16 is configured to approximatelyposition one eye of the user 12 on an optical axis of the imaging system10. For example, in the configuration shown in FIG. 1, the viewingassembly 16 is configured to approximately position the right eye of theuser 12 on the optical axis of the imaging system 10. In the illustratedembodiment, the viewing assembly 16 can be rotated 180 degrees around apivot axis 20 so as to reconfigure the viewing assembly 16 toapproximately position the left eye of the user 12 on the optical axisof the imaging system 10. Accordingly, each of the right and the lefteye of the user 12 can be selectively approximately positioned on theoptical axis of the imaging system 10 for imaging of the respective eyeby the imaging system 10. In embodiments described herein, finalpositioning and alignment of the optical axis of the respective eye ofthe user 12 with the optical axis of the imaging system 10 isaccomplished by the user 12 adjusting the user's position relative tothe view port 14 in response to feedback provided to the user 12 asdescribed herein.

FIG. 2 is a simplified schematic illustration of an embodiment of theophthalmic imaging system 10. In the illustrated embodiment, theophthalmic imaging system 10 includes a lens assembly 22, an ophthalmicimaging device 24, an eye camera 26, a display device 28, a control unit30, a suitable user interface 32, a first beam splitter 36, and a secondbeam splitter 38. The ophthalmic imaging device 24 has an optical axis40 to which the user 12 manually aligns a respective eye 42 of the user12 in response to feedback provided to the user 12 described herein. Thecontrol unit 30 includes a processor 33 and a data storage device 34. Afixation target 44 is displayed on the display device 28 and is viewableby the eye 42 via an optical path 46 that extends through the lensassembly 22 and is diverted by each of the first beam splitter 36 andthe second beam splitter 38. The display device 28, the first and secondbeam splitters 36, 38, and the position at which the fixation target 44is displayed on the display device 28 are configured so that the portionof the optical path 46 between the eye 42 and the first beam splitter 36aligns with the optical axis 40 of the imaging device 24 if the eye 42is fixated on the fixation target 44 and the optical center of the eye42 is positioned on the optical axis 40.

To generate the feedback to the user 12 to guide self-alignment of theoptical center of the eye 42 with the optical axis 40 of the imagingdevice 24, the eye camera 26 images the eye 42 to generate eye imagedata corresponding to the captured image of the eye 42. The eye imagedata is transmitted from the eye camera 26 to the control unit 30. Thecontrol unit 30 processes the eye image data to detect the opticalcenter of the eye 42 using any suitable approach. For example, in someembodiments, the control unit 30 processes the eye image data to detectthe pupil of the eye 42 and then processes the region of the image ofthe eye corresponding to the detected pupil to locate the center of thepupil. The location of the detected center of the pupil can then becompared with a known fixed location of the optical axis 40 to determinethe current relative position of the center of the eye 42 relative tothe optical axis 40.

In many embodiments, the display device 28 projects a relatively largebeam in the pupil plane (e.g., greater than 10 mm) in order to allow theuser to see the projection at every pupil position and correct the pupilposition accordingly. In many embodiments, the projection beam alwayscontain the pupil inside in order to avoid a situation that the usercannot see the display or partially sees it.

It should be obvious to a person skilled in the art that any suitableoptical assembly that includes the ophthalmic imaging device 24, the eyecamera 26, and the display device 28 can be employed in the ophthalmicimaging system 10. For example, FIG. 3 is a simplified schematicillustration of such a suitable optical assembly that includes theophthalmic imaging device 24, the eye camera 26, and the display device28 and can be employed in the ophthalmic imaging system 10. In theillustrated optical assembly, the ophthalmic imaging device 24 is aspectral domain OCT imaging device that operates in a wavelength rangeof 800 nm to 900 nm. The illustrated optical assembly includes an eyeilluminator 49 that illuminates the eye 42 using a suitable wavelengthof light (e.g., a wavelength of light above 920 nm). In the illustratedoptical assembly, the display device 28 can project light between anysuitable wavelength (e.g., from 400 nm to 700 nm). The illustratedoptical assembly includes a dichroic mirror 36 a that transmits the OCTwavelength and the display wavelength range (400 nm to 900 nm) andreflects the illumination wavelength (e.g., greater than 920 nm) to theeye camera 26. The illustrated optical assembly includes a dichroicmirror 38 a that transmits the display wavelength range and reflects theOCT wavelength.

In many embodiments, the control unit 30 generates a pseudo position ofthe eye 42 relative to the optical axis 40 as described herein withreference to FIG. 4 through FIG. 7 and displays an eye pseudo positionindicator 48 on the display device 28 so as to provide feedback to theuser 12 that the eye is located at the pseudo position of the eyerelative to the optical axis 40. Any suitable approach can be used toprovide the feedback to the user 12. For example, in many embodiments,the eye pseudo position indicator 48 is positioned on the display device28 relative to the fixation target 44 by the pseudo position of the eyerelative to the optical axis 40. In such embodiments, the fixationtarget 44 represents the location of the optical axis 40 and theposition of the eye pseudo position indicator 48 relative to thefixation target 44 provides feedback to the user 12 indicating if theuser 12 should reposition the user's eye relative to the view port 14,and if so, in what direction and by what distance.

In many embodiments, the control unit 30 is operatively coupled with,and controls operation of, the ophthalmic imaging device 24, the eyecamera 26, and the display device 28. For example, in many embodiments,the control unit 30 receives the eye image data from the eye camera 26and processes the eye image data to detect the location of the center ofthe eye 42 and determine the position of the center of the eye 42relative to the optical axis 40. In many embodiments, the optical axis40 is disposed at a fixed known position in an image of the eye capturedby the eye camera 26 and the position of the center of the eye 42 withinthe image of the eye is compared with the position of the optical axis40 within the image to determine the position of the center of the eye42 relative to the optical axis 40. In some embodiments, the controlunit 30 operates of the ophthalmic imaging device 24 when the center ofthe eye 42 is within an acceptable distance from the optical axis 40 andblocks operation of the ophthalmic imaging device 24 when the center ofthe eye 42 is not within an acceptable distance of the optical axis 40.

In many embodiments, the control unit 30 is part of a feedback loop thatprovides the feedback to the user 12 as described herein. For example,FIG. 4 is a simplified schematic illustration of an example feedbackloop 50 that provides the feedback described herein to the user 12 ofthe ophthalmic imaging device 24 regarding alignment of the user's eye42 with the optical axis 40 of the ophthalmic imaging system 10. In manyembodiments, the display device 28 displays an indication that is, inmany instances, offset from the actual position of the user's eye 42relative to the optical axis 40 by a controlled amount. By displaying anindication that is offset from the actual relative position of theuser's eye 42 by the controlled amount, the effort required by the user12 to achieve and maintain sufficient positioning of the user's eye 42relative to the optical axis 40 of the ophthalmic imaging device 24 maybe reduced relative to prior approaches.

In the illustrated embodiment of the feedback loop 50, the control unit30 includes a proportional controller 52 that generates a pseudoposition of the eye 42 (X′1, Y′ 1) from an actual position of the eye 42(X1, Y1) and the position of the optical axis 40 (X0, Y0). The controlunit 30 processes the eye image data from the eye camera 26 to determinethe actual position of the eye 42 (X1, Y1). In some embodiments, theproportional controller 52 multiplies differences between actualposition of the eye 42 (X1, Y1) and the position of the optical axis 40(X0, Y0) by a predefined factor, referred to below as gain factor (G).For example, in some embodiments: (a) (X′1, Y′1) are the coordinatessent to the display device 28 from the proportional controller 52 atwhich the eye pseudo position indicator 48 is displayed to the user 12,(b) (X′0, Y′0)=(X0, Y0) (correspond to the location of the optical axis40 of the imaging device 24 and the fixation target 44 displayed to theuser 12), (c) (X1, Y1) are the coordinates of the actual position of thecenter of the eye 42 relative to the optical axis 40 of the imagingdevice 24, (d) X′1=X0+(X1−X0)*G is the x-coordinate of the eye pseudoposition indicator 48 displayed to the user 12 on the display device 28,and (e) Y′1=Y0+(Y1−Y0)*G is the y-coordinate of the eye pseudo positionindicator 48 displayed to the user 12 on the display device 28. Anexample display for a G=1.5 is shown in FIG. 5.

In many embodiments, if the eye 42 is not exactly positioned on theoptical axis 40 of the ophthalmic imaging device 24, but isnone-the-less positioned within an acceptable distance from the opticalaxis 40, the eye pseudo position indicator 48 is displayed on thedisplay device 28 so as to give a false feedback to the user 12 that theeye 42 is centered on the optical axis 40. For example, as shown in FIG.6, when the actual relative position of the pupil is within anacceptable pupil position boundary 54 (not actually displayed to theuser in many embodiments), the eye pseudo position indicator 48 isdisplayed on the display device 28 aligned with the fixation target 44,thereby serving to inhibit the user 12 from further repositioning of theuser's eye 42 relative to the view port 14. In many embodiments, thedisplayed location of the eye position pseudo indicator 48 changessuddenly when the position of the eye 42 is repositioned from outside ofthe acceptable pupil position boundary 54 to within the boundary 54,thereby appearing to the user 12 to snap between the displayedpositions.

For example, in some embodiments the control unit 30 is configured tocheck if the current position of the eye 42 is within the acceptablepupil position boundary 54 relative to the optical axis 40 of theophthalmic imaging device 24. If the current position of the eye 42 iswithin the acceptable pupil position boundary 54, then the control unit30 sets X′1=X′0 and Y′1=Y′0 so that the eye pseudo position indicator 48is placed on the fixation target 44. In other words, when the eye 42 iswithin a distance D of the optical axis 40 of the ophthalmic imagingdevice 24 (i.e., ((X1−X0){circumflex over ( )}2±(Y1−Y0){circumflex over( )}2){circumflex over ( )}0.5<=D), then X′1=X′0 and Y′1=Y′0.

In some embodiments, the size of the acceptable pupil position boundary54 is a function of the size of the pupil of the eye 42. For example, insome embodiments, the acceptable pupil position boundary is smaller fora relatively small pupil and larger for a relatively large pupil. Insome embodiments, the size of the acceptable pupil position boundary 54can be based in imaging requirements, which can be changed from one userto another, from one test to another, and/or from one disease state toanother.

In some embodiments, the ophthalmic imaging system 10 is configured todetect when the user 12 is having trouble achieving and/or maintainingacceptable positioning of the user's eye 42 relative to the optical axis40 of the ophthalmic imaging device 24. In response to detecting theuser 12 having difficulty achieving and/or maintaining acceptablepositioning of the user's eye 42 relative to the optical axis 40, thefeedback provided to the user 12 via the display device can be modifiedto further assist the user 12. For example, the size of the fixationtarget 44 can be increased and/or the size of the eye pseudo positionindicator 48 can be increased, which may further assist a user that haspoor vision. Any suitable approach can be used to detect when the user12 is having trouble achieving and/or maintaining acceptable positioningof the user's eye 42 relative to the optical axis 40. For example, ifthe user 12 fails to achieve acceptable positioning of the user's eye 42relative to the optical axis 40 within a suitable time period and/orfails to maintain the eye 42 within the acceptable pupil positionboundary 54 for a suitable time period, the system 10 can make adetermination that the user 12 is having trouble positioning the eye 42relative to the optical axis 40 and make suitable modifications to thefeedback provided to the user 12, such as those modifications describedherein, to aid the user's efforts.

In some embodiments, the control unit 30 is configured to detect theposition of the eye 42 even if a portion of the pupil of the eye 42 isobscured (for example, when a drooped eye lid obscures a portion of thepupil). For example, in some embodiments, the control unit 30 processesthe eye image data to detect if a portion of a pupil of the eye 42 isobscured. If a portion of the pupil of the eye 42 is obscured, thecontrol unit 30 can identify an unobscured portion of the pupil, anddetermine the position of the eye 42 relative to the optical axis 40based on the unobscured portion of the pupil.

In some embodiments, the control unit 30 is configured to display theactual position of the eye 42 relative to the optical axis 40. Forexample, the control unit 30 can be configured to cause the actualrelative position of the pupil to be displayed at (X1, Y1) (see FIG. 4).

FIG. 7 is a simplified schematic block diagrams of acts of a method 100of providing feedback to a user of an ophthalmic imaging systemregarding alignment of an eye of the user with an optical axis of theophthalmic imaging system, in accordance with some embodiments. Anysuitable ophthalmic imaging system, such as the ophthalmic imagingsystem 10 described herein, can be employed in the practice of themethod 100. In the method 100, a fixation target is displayed to a useron a display device (act 102). Eye image data corresponding to an imageof the eye viewing the fixation target is generated (act 104). The eyeimage data is processed to determine a position of the eye relative tothe optical axis (act 106). A pseudo position of the eye relative to theoptical axis is generated based on the position of the eye relative tothe optical axis (act 108). An indication is displayed on the displaydevice to provide feedback to the user indicating that the eye islocated at the pseudo position of the eye relative to the optical axis(act 110).

FIG. 8 is a simplified schematic block diagrams of additional acts thatcan be practiced in the method 100, in accordance with some embodiments.In act 112, if the position of the eye is within an acceptable distancefrom the optical axis, the pseudo position of the eye can be set to lieon the optical axis. In act 114, the acceptable distance is determinedbased on a size of the pupil of the user's eye. In act 116, the eyeimage data is processed to determine the size of the pupil of the user'seye. In act 118, the position of the eye is based on a portion of thepupil excluding an obscured portion of the pupil. In act 120, the pseudoposition of the eye relative to the optical axis is repeatedly updatedfor each of a series of images of the eye. In act 122, a series ofimages of the eye is processed to detect if the user fails to achieveand/or maintain acceptable positioning of the eye relative to theoptical axis.

In some embodiments of the ophthalmic imaging system 10, the acceptabledistance is increased in response to user 12 achieving an initialacceptable alignment of the eye 42 with the optical axis 40. Forexample, FIG. 9 illustrates a pre-alignment acceptable alignment area 56and a post-alignment acceptable area 58 relative to an imaging area 60of the ophthalmic imaging system 10. The acceptable distance is setequal to a pre-alignment acceptable distance (corresponding to thepre-alignment acceptable alignment area 56) prior to the position of theeye being repositioned from being greater than the pre-alignmentacceptable distance from the optical axis 40 to being equal to or lessthan the pre-alignment acceptable distance from the optical axis 40. Theacceptable distance is then reset to a post-alignment acceptabledistance (corresponding to the post-alignment acceptable alignment area58) in response to the position of the eye being repositioned from beinggreater than the pre-alignment acceptable distance from the optical axis40 to being equal to or less than the pre-alignment acceptable distancefrom the optical axis 40. The post-alignment acceptable distance isgreater than the pre-alignment acceptable distance. By allowing the userincreased movement following achievement of the initial acceptablealignment of the user's eye 42 with the optical axis 40, the user ispresented with decreased repositioning commands, and thereby experiencesa more stable imaging session. The diameters of the pre-alignmentacceptable alignment area 56 and the post-alignment acceptable area 58can be based on the size of the pupil 62. For example, if the pupil 62is relatively large, the diameters of the pre-alignment acceptablealignment area 56 and the post-alignment acceptable area 58 can beincreased relative to those for smaller pupils so as to enable quickeralignment and improved experience for the user. Alternatively, thediameters of the pre-alignment acceptable alignment area 56 and thepost-alignment acceptable area 58 can be based on size of the smallestpupil expected in a selected population of users.

In some embodiments of the ophthalmic imaging system 10, the controlunit is configured to guide the user 12 to position the user's pupilbased on an unobscured portion of the pupil instead of the center of thepupil. By guiding the user to position the user's pupil based on theunobscured portion of the pupil, blocking of the OCT imaging beam by theuser's eyelid can be reduced. For example, FIG. 10 illustrates anacceptable alignment area 64 for a partially obscured pupil relative tothe imaging area 60 of the ophthalmic imaging system 10. The acceptablealignment area 64 is shaped to overlay an unobstructed portion of apartially obscured pupil relative to the imaging area 60 of theophthalmic imaging system 10. In many existing ophthalmic imagingsystems, a pupil detection algorithm is employed that processes an imageof the eye to identify the pupil by searching for a black circle oralmost black circle feature in the image of the eye; the imaging beam isthen aligned with the center of the pupil. The use of such an existingapproach with an elderly user having a droopy eyelid, however, canresult in a significant percentage of the light beam being blocked bythe user's eyelid and the resulting OCT signal may be very weak ornonexistent. By shaping the acceptable alignment area 64 to overlay anunobstructed portion of a partially obscured pupil relative to theimaging area 60, the user 12 is provided feedback to align the imagingarea 60 with the unobstructed portion of the user's pupil, therebyavoiding blockage of the OCT imaging beam via the user's eyelid. Asanother example, FIG. 11 illustrates that the pre-alignment acceptablealignment area 56 and the post-alignment acceptable alignment area 58can be shaped to overlay an unobstructed portion of a partially obscuredpupil.

Other variations are within the spirit of the present invention. Thus,while the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

Examples of the embodiments of the present disclosure can be describedin view of the following clauses:

Clause 1. An ophthalmic imaging system, comprising an ophthalmic imagingdevice having an optical axis, a display device displaying a fixationtarget viewable by an eye of a user, an eye camera operable to image theeye to generate eye image data, and a control unit. The control unitprocesses the eye image data to determine a position of the eye relativeto the optical axis. The control unit processes the position of the eyerelative to the optical axis to generate a pseudo position of the eyerelative to the optical axis. The pseudo position of the eye relative tothe optical axis is different from the position of the eye relative tothe optical axis. The control unit causes the display device to displayan indication that provides feedback to the user that the eye is locatedat the pseudo position of the eye relative to the optical axis.

Clause 2. The ophthalmic imaging system of clause 1, comprising a viewport that is coupled to the ophthalmic imaging device.

Clause 3. The ophthalmic imaging system of any preceding clause, whereinthe indication displayed to the user comprises an eye pseudo positionindicator displayed at a position relative to the fixation targetmatching the pseudo position of the eye relative to the optical axis.

Clause 4. The ophthalmic imaging system of any preceding clause,wherein, if a distance between the position of the eye and the opticalaxis is less than an acceptable distance, the pseudo position of the eyerelative to the optical axis is generated to lie on the optical axis.

Clause 5. The ophthalmic imaging system of clause 4, wherein theindication displayed to the user comprises an eye pseudo positionindicator displayed aligned with the fixation target to provide feedbackto the user indicating that the position of the eye is located on theoptical axis.

Clause 6. The ophthalmic imaging system of clause 4, wherein theacceptable distance is based on a size of a pupil of the eye.

Clause 7. The ophthalmic imaging system of clause 6, wherein the controlunit processes the eye image data to determine the size of the pupil ofthe eye.

Clause 8. The ophthalmic imaging system of clause 4, wherein theacceptable distance is equal to a pre-alignment acceptable distanceprior to the position of the eye being repositioned from being greaterthan the pre-alignment acceptable distance from the optical axis tobeing equal to or less than the pre-alignment acceptable distance fromthe optical axis, and the acceptable distance is set to a post-alignmentacceptable distance in response to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis, thepost-alignment acceptable distance being greater than the pre-alignmentacceptable distance.

Clause 9. The ophthalmic imaging system of clause 8, wherein thepre-alignment acceptable distance is based on a size of a pupil of theeye and/or the post-alignment acceptable distance is based on a size ofa pupil of the eye.

Clause 10. The ophthalmic imaging system of clause 9, wherein thecontrol unit processes the eye image data to determine the size of thepupil of the eye.

Clause 11. The ophthalmic imaging system of any preceding clause,wherein the control unit is configured to process the eye image data todetect if a portion of a pupil of the eye is obscured, identify anunobscured portion of the pupil, and determine the position of the eyerelative to the optical axis based on the unobscured portion of thepupil.

Clause 12. The ophthalmic imaging system of clause 11, wherein if adistance between the position of the eye and to the optical axis is lessthan an acceptable distance, the pseudo position of the eye relative tothe optical axis is generated to lie on the optical axis.

Clause 13. The ophthalmic imaging system of clause 12, wherein theacceptable distance is equal to a pre-alignment acceptable distanceprior to the position of the eye being repositioned from being greaterthan the pre-alignment acceptable distance from the optical axis tobeing equal to or less than the pre-alignment acceptable distance fromthe optical axis, and the acceptable distance is set to a post-alignmentacceptable distance in response to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis, thepost-alignment acceptable distance being greater than the pre-alignmentacceptable distance.

Clause 14. The ophthalmic imaging system of clause 13, wherein thepre-alignment acceptable distance is based on a size of a pupil of theeye and/or the post-alignment acceptable distance is based on a size ofa pupil of the eye.

Clause 15. The ophthalmic imaging system of clause 14, wherein thecontrol unit processes the eye image data to determine the size of thepupil of the eye.

Clause 16. The ophthalmic imaging system of any preceding clause,wherein the eye camera captures a series of images of the eye, and theeye image data comprises image data for each of the series of images ofthe eyes. For each image of the series of images of the eye, the controlunit processes the eye image data to determine a respective position ofthe eye relative to the optical axis, and processes the respectiveposition of the eye relative to the optical axis to generate arespective pseudo position of the eye relative to the optical axis. Therespective pseudo position of the eye relative to the optical axis beingdifferent from the respective position of the eye relative to theoptical axis. For each image of the series of images, the control unitcauses the display device to display a respective indication thatprovides feedback to the user that the eye is located at the respectivepseudo position of the eye relative to the optical axis.

Clause 17. The ophthalmic imaging system of clause 16, wherein thecontrol unit processes, for the series of images of the eye, a series ofpositions of the eye relative to the optical axis to detect if the userfails to achieve and/or maintain acceptable positioning of the eyerelative to the optical axis. The control unit, in response to detectingfailure of the user to achieve and/or maintain acceptable positioning ofthe eye relative to the optical axis, increases a size of the fixationtarget and/or the indication displayed to the user that provides thefeedback to the user.

Clause 18. The ophthalmic imaging system of any preceding clause,wherein the control unit comprises a proportional controller, andgeneration of the pseudo position of the eye relative to the opticalaxis by the control unit comprises multiplying, by the proportionalcontroller, the position of the eye relative to the optical axis by again factor not equal to 1.0.

Clause 19. The ophthalmic imaging system of clause 18, wherein, if adistance between the position of the eye and the optical axis is lessthan an acceptable distance, the pseudo position of the eye relative tothe optical axis is generated to lie on the optical axis.

Clause 20. The ophthalmic imaging system of clause 19, wherein theindication displayed to the user comprises an eye pseudo positionindicator displayed aligned with the fixation target to provide feedbackto the user indicating that the eye is located on the optical axis.

Clause 21. The ophthalmic imaging system of clause 19, wherein theacceptable distance is equal to a pre-alignment acceptable distanceprior to the position of the eye being repositioned from being greaterthan the pre-alignment acceptable distance from the optical axis tobeing equal to or less than the pre-alignment acceptable distance fromthe optical axis, and the acceptable distance is set to a post-alignmentacceptable distance in response to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis, thepost-alignment acceptable distance being greater than the pre-alignmentacceptable distance.

Clause 22. The ophthalmic imaging system of any preceding clause,wherein the ophthalmic imaging device comprises a spectral domainoptical coherence tomography (OCT) imaging device that operates in awavelength range of 800 nm to 900 nm, and the display device projectslight in a wavelength range of 400 nm to 800 nm. The ophthalmic imagingsystem comprises an eye illuminator, a first dichroic mirror, and asecond dichroic mirror. The eye illuminator illuminates the eye withlight including a wavelength greater than 920 nm. The first dichroicmirror transmits light in a wavelength range of 400 nm to 900 nm andreflects light with a wavelength above 920 nm. The second dichroicmirror transmits light in a wavelength range between 400 nm to 800 nmand reflects light in a wavelength range between 800 nm and 900 nm.

Clause 23. The ophthalmic imaging system of any preceding clause,wherein the display device projects a beam in the plane of the pupilthat extends beyond a 10 mm diameter circle.

Clause 24. A method of providing feedback to a user of an ophthalmicimaging system regarding alignment of an eye of the user with an opticalaxis of the ophthalmic imaging system. The method comprises displaying afixation target on a display device viewable by the eye of the user;generating, by an eye camera, eye image data corresponding to an imageof the eye viewing the fixation target; processing the eye image data,by a control unit, to determine a position of the eye relative to theoptical axis; generating, by the control unit, a pseudo position of theeye relative to the optical axis based on the position of the eyerelative to the optical axis, the pseudo position of the eye relative tothe optical axis being different from the position of the eye relativeto the optical axis; and causing, by the control unit, display of anindication on the display device to provide feedback to the userindicating that the eye is located at the pseudo position of the eyerelative to the optical axis.

Clause 25. The method of clause 24, wherein display of the indication onthe display device comprises display of an eye pseudo position indicatorat a position relative to the fixation target matching the pseudoposition of the eye relative to the optical axis.

Clause 26. The method of any of clause 24 and clause 25, furthercomprising processing the position of the eye relative to the opticalaxis to determine if a distance between the position of the eye and theoptical axis is less than an acceptable distance, and wherein, if thedistance between the position of the eye and the optical axis is lessthan the acceptable distance, the generation of the pseudo position ofthe eye relative to the optical axis comprises setting the pseudoposition of the eye to lie on the optical axis.

Clause 27. The method of clause 26, wherein the display of theindication on the display device comprises displaying an eye pseudoposition indicator aligned with the fixation target to provide feedbackto the user that the eye is located on the optical axis.

Clause 28. The method of clause 27, further comprising determining theacceptable distance based on a size of a pupil of the eye.

Clause 29. The method of clause 28, further comprising processing theeye image data, by the control unit, to determine the size of the pupilof the eye.

Clause 30. The method of any of clause 26 through clause 29, wherein theacceptable distance is equal to a pre-alignment acceptable distanceprior to the position of the eye being repositioned from being greaterthan the pre-alignment acceptable distance from the optical axis tobeing equal to or less than the pre-alignment acceptable distance fromthe optical axis, and the acceptable distance is set to a post-alignmentacceptable distance in response to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis, thepost-alignment acceptable distance being greater than the pre-alignmentacceptable distance.

Clause 31. The method of clause 30, further comprising determining thepre-alignment acceptable distance and/or the post-alignment acceptabledistance based on a size of a pupil of the eye.

Clause 32. The method of clause 31, further comprising processing theeye image data, by the control unit, to determine the size of the pupilof the eye.

Clause 33. The method of any of clause 24 through clause 32, furthercomprising processing the eye image data, by the controller, to detectif a portion of a pupil of the eye is obscured, identify an unobscuredportion of the pupil, and determine the position of the eye relative tothe optical axis based on the unobscured portion of the pupil.

Clause 34. The method of clause 33, wherein if a distance between theposition of the eye and the optical axis is less than an acceptabledistance, the pseudo position of the eye relative to the optical axis isgenerated to lie on the optical axis.

Clause 35. The method of clause 34, wherein the acceptable distance isequal to a pre-alignment acceptable distance prior to the position ofthe eye being repositioned from being greater than the pre-alignmentacceptable distance from the optical axis to being equal to or less thanthe pre-alignment acceptable distance from the optical axis, and theacceptable distance is set to a post-alignment acceptable distance inresponse to the position of the eye being repositioned from beinggreater than the pre-alignment acceptable distance from the optical axisto being equal to or less than the pre-alignment acceptable distancefrom the optical axis, the post-alignment acceptable distance beinggreater than the pre-alignment acceptable distance.

Clause 36. The method of clause 35, further comprising determining thepre-alignment acceptable distance and/or the post-alignment acceptabledistance based on a size of a pupil of the eye.

Clause 37. The method of clause 36, further comprising processing theeye image data, by the control unit, to determine the size of the pupilof the eye.

Clause 38. The method of any of clause 24 through clause 37, comprisinggenerating, by the eye camera, the eye image data so as to compriseimage data for each of a series of images of the eyes. The methodfurther comprising, for each image of the series of images of the eye,processing the eye image data, by the control unit, to determine arespective position of the eye relative to the optical axis; processingthe respective position of the eye relative to the optical axis, by thecontrol unit, to generate a respective pseudo position of the eyerelative to the optical axis, the respective pseudo position of the eyerelative to the optical axis being different from the respectiveposition of the eye relative to the optical axis; and causing, by thecontrol unit, the display device to display a respective indication thatprovides feedback to the user that the eye is located at the respectivepseudo position of the eye relative to the optical axis.

Clause 39. The method of clause 38, comprising processing, by thecontrol unit, for the series of images of the eye, a series of positionsof the eye relative to the optical axis to detect if the user fails toachieve and/or maintain acceptable positioning of the eye relative tothe optical axis; and in response to detecting, by the control unit,failure of the user to achieve and/or maintain acceptable positioning ofthe eye relative to the optical axis, increasing, by the control unit, asize of the fixation target and/or the indication displayed to the userthat provides the feedback to the user.

Clause 40. The method of any of clause 24 through clause 39, wherein thegeneration of the pseudo position of the eye relative to the opticalaxis comprises multiplying the position of the eye relative to theoptical axis by a factor not equal to 1.0.

Clause 41. The method of clause 40, wherein, if a distance of the eyerelative to the optical axis is less than an acceptable distance, thepseudo position of the eye relative to the optical axis is generated tolie on the optical axis.

Clause 42. The method of clause 41, wherein the indication displayed tothe user comprises an eye pseudo position indicator displayed alignedwith the fixation target to provide feedback to the user that the eye islocated on the optical axis.

Clause 43. The method of any of clause 41 and clause 42, wherein theacceptable distance is equal to a pre-alignment acceptable distanceprior to the position of the eye being repositioned from being greaterthan the pre-alignment acceptable distance from the optical axis tobeing equal to or less than the pre-alignment acceptable distance fromthe optical axis; and the acceptable distance is set to a post-alignmentacceptable distance in response to the position of the eye beingrepositioned from being greater than the pre-alignment acceptabledistance from the optical axis to being equal to or less than thepre-alignment acceptable distance from the optical axis, thepost-alignment acceptable distance being greater than the pre-alignmentacceptable distance.

Clause 44. An ophthalmic imaging system, compromising an ophthalmicimaging device having an optical axis, a display device displaying afixation target viewable by an eye of a user, an eye camera operable toimage the eye to generate eye image data, and a control unit. Thecontrol unit processes the eye image data to determine a position of theeye relative to the optical axis, and causes the display device todisplay an indication that provides feedback to the user that the eye islocated at the position of the eye relative to the optical axis.

What is claimed is:
 1. A method of providing feedback to a user of an ophthalmic imaging system regarding alignment of an eye of the user with an optical axis of the ophthalmic imaging system, the method comprising: displaying a fixation target on a display device viewable by the eye of the user; generating, by an eye camera, eye image data corresponding to an image of the eye viewing the fixation target; processing the eye image data, by a control unit, to determine a position of the eye relative to the optical axis; generating, by the control unit, a pseudo position of the eye relative to the optical axis based on the position of the eye relative to the optical axis, the pseudo position of the eye relative to the optical axis being different from the position of the eye relative to the optical axis; processing the position of the eye relative to the optical axis to determine if a distance between the position of the eye and the optical axis is less than an acceptable distance; wherein, if the distance between the position of the eye and the optical axis is less than the acceptable distance, the generation of the pseudo position of the eye relative to the optical axis comprises setting the pseudo position of the eye to lie on the optical axis; wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis; and wherein the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance; and causing, by the control unit, display of an indication on the display device to provide feedback to the user indicating that the eye is located at the pseudo position of the eye relative to the optical axis.
 2. The method of claim 1, wherein display of the indication on the display device comprises display of an eye pseudo position indicator at a position relative to the fixation target matching the pseudo position of the eye relative to the optical axis.
 3. The method of claim 1, wherein the display of the indication on the display device comprises displaying an eye pseudo position indicator aligned with the fixation target to provide feedback to the user that the eye is located on the optical axis.
 4. The method of claim 1, further comprising determining the pre-alignment acceptable distance and/or the post-alignment acceptable distance based on a size of a pupil of the eye.
 5. The method of claim 4, further comprising processing the eye image data, by the control unit, to determine the size of the pupil of the eye.
 6. The method of claim 1, comprising: generating, by the eye camera, the eye image data so as to comprise image data for each of a series of images of the eyes; and for each image of the series of images of the eye: processing the eye image data, by the control unit, to determine a respective position of the eye relative to the optical axis; processing the respective position of the eye relative to the optical axis, by the control unit, to generate a respective pseudo position of the eye relative to the optical axis, the respective pseudo position of the eye relative to the optical axis being different from the respective position of the eye relative to the optical axis; and causing, by the control unit, the display device to display a respective indication that provides feedback to the user that the eye is located at the respective pseudo position of the eye relative to the optical axis.
 7. The method of claim 6, comprising: processing, by the control unit, for the series of images of the eye, a series of positions of the eye relative to the optical axis to detect if the user fails to achieve and/or maintain acceptable positioning of the eye relative to the optical axis; and in response to detecting, by the control unit, failure of the user to achieve and/or maintain acceptable positioning of the eye relative to the optical axis, increasing, by the control unit, a size of the fixation target and/or the indication displayed to the user that provides the feedback to the user.
 8. The method of claim 1, wherein the generation of the pseudo position of the eye relative to the optical axis comprises multiplying the position of the eye relative to the optical axis by a factor not equal to 1.0.
 9. The method of claim 1, further comprising processing the eye image data, by the controller, to: detect if a portion of a pupil of the eye is obscured; identify an unobscured portion of the pupil; and determine the position of the eye relative to the optical axis based on the unobscured portion of the pupil.
 10. The method of claim 9, wherein the display device projects a beam in the plane of the pupil that extends beyond a 10 mm diameter circle.
 11. The method of claim 1, wherein the display device projects a beam in the plane of the pupil of the eye that extends beyond a 10 mm diameter circle. 